ADS-B In receives traffic, weather, and flight data from nearby aircraft and FAA ground stations — and puts it all in the cockpit with no subscription.
Most pilots know ADS-B Out is mandatory in controlled airspace, but the inbound side of the system is where the cockpit gets its biggest upgrade. How does ADS-B In work? It listens for broadcasts on two radio frequencies — 1090 MHz position reports from aircraft and 978 MHz weather and traffic data from FAA ground stations — then displays the combined picture on a moving map. The whole system runs without a monthly bill, and the hardware can cost less than a tablet.
What ADS-B In Actually Does
ADS-B In is the receive half of the Automatic Dependent Surveillance–Broadcast system. While ADS-B Out transmits your aircraft’s GPS position, altitude, speed, and identification every second, ADS-B In listens for those same broadcasts from nearby aircraft and for data uplinked from FAA ground stations.
The result is a real-time traffic picture of aircraft around you — displayed as targets with altitude, speed, and heading — plus free weather imagery and flight information. No interrogation signal is needed. The data is simply broadcast, and any properly equipped receiver within range can pick it up.
How Does ADS-B In Receive Traffic And Weather?
ADS-B In uses two radio frequencies, and each carries different data. Aircraft equipped with 1090 MHz Extended Squitter (1090ES) transponders broadcast their position once per second. An ADS-B In receiver tuned to 1090 MHz picks up those reports directly from other aircraft — that is the traffic picture.
For weather and supplemental traffic, FAA ground stations transmit on 978 MHz using the Universal Access Transceiver (UAT) format. These stations broadcast NEXRAD radar imagery, METARs, TAFs, NOTAMs, and TIS-B traffic data that includes aircraft without ADS-B Out. The FAA’s network of roughly 800 ground stations provides this coverage across most of the continental United States.
The 978 MHz UAT channel carries the richest free data, but it is only available in the United States. International flights use 1090 MHz for both transmission and reception. For the full technical breakdown, the FAA’s official breakdown of ADS-B In capabilities covers the performance standards and frequency rules in detail.
ADS-B Out vs. In: What’s Mandatory And What’s Optional
ADS-B Out is the legally required component. ADS-B In is entirely optional — but it is where the pilot gets direct value from the system.
| Feature | ADS-B Out | ADS-B In |
|---|---|---|
| Primary Function | Broadcasts position, altitude, speed, and ID to ATC | Receives traffic, weather, and flight data |
| Mandatory? | Yes — required in most controlled airspace under 14 CFR 91.225 | No — entirely optional |
| Required Equipment | ADS-B transponder + WAAS GPS source | Receiver, processor, and cockpit display |
| Data Type | GPS position, altitude, ground speed, aircraft ID | TIS-B traffic, FIS-B weather, NOTAMs, advisories |
| Frequency Options | 1090ES or 978 MHz UAT | 1090ES and/or 978 MHz UAT |
| Update Rate | 1 Hz (once per second) | 1 Hz (once per second) |
| Typical Cost (GA) | $2,000–$5,000 | $500–$3,000 |
| Subscription | None required | None required |
What Hardware Do You Need For ADS-B In?
ADS-B In needs three things: an antenna and receiver tuned to the right frequency, a data processor, and a cockpit display. Many modern avionics suites — such as the Garmin G3X or Aspen E1000 — handle all three when paired with an appropriate receiver module.
For aircraft without integrated avionics, portable receivers like the Stratus and Sentry pick up both frequencies and stream traffic and weather over Wi-Fi or Bluetooth to a tablet running ForeFlight or Garmin Pilot. These portable units cost $500–$1,000 and take minutes to install.
If you are evaluating options, our roundup of the best ADS-B In receivers compares portable and panel-mount models tested in real flying conditions.
Where ADS-B In Works And Where It Doesn’t
The FAA’s ground station network covers most controlled airspace and the route structure between major cities. Remote mountain areas and stretches of open water have gaps where no ground-based signal reaches. In those regions, aircraft with a 1090 MHz antenna can still receive traffic from other aircraft within radio range, but the weather uplink is unavailable.
Space-based ADS-B via the Aireon network on Iridium NEXT satellites extends coverage globally, including over oceans. The satellite data is primarily used for ATC surveillance, but some receivers can access space-based traffic data as well.
A practical limitation: the 978 MHz UAT weather and TIS-B data is US-only. Outside the US, ADS-B In on 1090 MHz will show traffic from other equipped aircraft, but the free FAA weather broadcast is absent.
What Data ADS-B In Puts In The Cockpit
The actual data a pilot sees depends on the receiver and display setup, but the FAA broadcasts the following information on the 978 MHz UAT and through direct 1090 MHz reception.
| Data Type | What It Shows | Source |
|---|---|---|
| Traffic (TIS-B) | Nearby aircraft position, altitude, heading, and ground speed | ATC radar and ADS-B rebroadcast via ground stations |
| Weather (FIS-B) | NEXRAD imagery, METARs, TAFs, winds aloft, icing reports, PIREPs | FAA ground stations on 978 MHz |
| Status Reports | NOTAMs, TFRs, Special Use Airspace activation status | FAA data feed via ground uplink |
| Airport Conditions | AWOS/ASOS reports, runway surface state, density altitude | Automated airport sensors |
| Flight Advisories | SIGMETs, AIRMETs, convective outlooks, center weather alerts | National Weather Service via FAA |
Together, these data streams give a pilot a complete picture of the operating environment — all delivered without a subscription. The hardware is a one-time purchase, and every weather report, traffic target, and advisory is free from that point forward.
FAQs
Is ADS-B In mandatory or optional?
ADS-B In is completely optional. Only ADS-B Out is required by the FAA for operation in most controlled airspace under 14 CFR 91.225. Many pilots add ADS-B In specifically for the free weather and traffic data, but it is never legally required.
Can I receive ADS-B data on a tablet or phone?
Yes. Portable ADS-B receivers like the Stratus and Sentry connect to iPads and Android tablets over Wi-Fi or Bluetooth. Apps such as ForeFlight and Garmin Pilot display the traffic and weather data on a moving map without any panel integration required.
Does ADS-B In work outside the United States?
Partially. ADS-B In on 1090 MHz will receive traffic from other equipped aircraft anywhere within radio range. However, the FAA’s free weather broadcast (FIS-B) and traffic rebroadcast (TIS-B) on 978 MHz UAT are only available in US airspace. International pilots rely on 1090 MHz reception for traffic only.
Is there a monthly fee for ADS-B In weather data?
No. The FAA broadcasts weather and traffic data on the 978 MHz UAT frequency at no charge. Once you own the receiver hardware, there are no subscription costs for FIS-B weather, TIS-B traffic, or NOTAMs. This is one of the system’s primary advantages over subscription-based weather services.
What is the difference between TIS-B and FIS-B?
TIS-B (Traffic Information Service – Broadcast) provides positions of nearby aircraft that do not have ADS-B Out, rebroadcast from ATC radar. FIS-B (Flight Information Service – Broadcast) delivers weather products including NEXRAD, METARs, TAFs, winds aloft, and icing reports. Both are transmitted on 978 MHz UAT and received with the same ADS-B In hardware.
References & Sources
- FAA. “ADS-B In Capabilities.” Official FAA breakdown of ADS-B In functions, frequencies, and performance requirements.